This invention relates to electrical connectors, and more particularly, connectors for electrically connecting a cylindrical member, such as a bolt, a rod, a cable, screw or stud, to a circuit, e.g., electronic seal locking devices.
Cargo shipping vehicles, cargo shipping containers and rail cars are subject to widespread tampering due to the value of the cargo. The rail cars, vehicles and containers have doors which are locked shut with hasps and secured with locking seals. Such seals include a steel bolt having a head and shank which is attached to a locking body having a shank locking mechanism. When the shank is inserted into the body, a locking collet or other arrangement permanently locks the shank to the body. For example, reference is made to commonly owned U.S. Pat. Nos. 5,005,883, 5,127,687, 4,802,700, 5,347,689, 5,413,393 and others for the disclosure of various seals of the type described.
Cargo containers are shipped via boat, train and truck. Hundreds of containers may be on a single boat. When the containers are unloaded they may be subject to tampering and vandalism. It is important that such tampering be immediately noted to preclude theft of valuable cargo. To assist in such theft and tampering prevention, prior art seals are assigned serial numbers. These seals are then assigned to a container and lock the assigned container. The serial number, container number, the carrier, and the location are then entered into a local computer manually. The entry then is manually made to show that the container is being shipped out of that location. Should a seal be tampered with, the event may be discovered at a different time and different location.
An electronic tagging device is commercially available that is programmable and which transmits information that is programmed, such as tagging identification serial numbers and other information as desired. This information is transmitted via radio frequency and is referred to as radio frequency identification (RFID) which is well known in the art. The aforementioned copending application discloses an embodiment of such a seal. However, the seal disclosed in that application comprises a plurality of contacts for engagement with the bolt, each contact at one contact point on the bolt and which contacts complete the circuit in the seal. The seal becomes electrically operative after the bolt is inserted and locked to the seal.
In that embodiment, a problem was encountered in which the contacts periodically would become disengaged from the bolt causing the generation of false tampering signals. Those contacts are S-shaped and spring loaded so that when compressed the contact resiliently engages the bolt. Still such a contact was found not satisfactory due to intermittent engagement due to vibrations and the like during use.
The present inventors recognize a need for a contact that solves the above identified problem with the prior art contacts previously used in such electronic seals.
U.S. Pat. No. 1,697,954 discloses an electrical connector having an aperture for accommodating a bolt. The connector may have external or internal teeth. The teeth are warped. The teeth prevent the backing off of a binding nut attached to the bolt. The teeth dig into the metal when the nut is tightened to improve the electrical contact. The nut when tightened stresses the teeth and flattens them. The effect is the same whether the teeth are radially inward or outward, with the inward direction preferred to save metal. This connector is not useful with a bolt used for seals which must engage the electrical connector without a nut. The patent does not describe the teeth as engaging the bolt for electrical contact with the bolt without the presence of a nut. The bolt thus can not engage the connector electrically without the use of a nut which is not desirable in an electronic seal of the type described above. This connector is not useful for such a seal and coupled bolt.
U.S. Pat. No. 2,321,158 discloses a connector telescopically associated with a stud to secure the stud against axial movement with respect to an associated workpiece and also to serve as an electrical terminal. Inner teeth are forced into engagement with the stud with a tool and by application of a force on the outer margin of the connector with a tool the teeth may be released. This connector is not useful for a seal of the type disclosed as it requires access to the connector margin to release the connector and also, such release is not desirable after the bolt is locked. The contact in the electronic seal described above herein is located inside of the seal housing and access to the contact is not possible with engagement or disengagement tools once the locking bolt is locked to the housing. Such access is not desirable as it would permit access to tampering tools inside of the seal housing. Further, a fastening tool is required by the patent to embed the connector teeth into the stud. To loosen the connector requires pressure at the outer edges of the of the rim of the connector with a tool. This connector is not operative with the electronic seal of the type described above herein.
U.S. Pat. Nos. 2,342,170, 2,342,312 and 2,394,728 to Tinnerman disclose fastening devices designed to serve as a nut for use with a threaded screw. The devices comprise a sheet metal spring plate member designed for use with a threaded bolt or screw to provide relatively quick fastening to the bolt or screw. The devices are currently well known in industry as Tinnerman fasteners. These devices are not known as electrical connectors and are not normally used as such. The devices have thread engaging means for engaging the threads of the bolt or screw. These devices are not described as or designed for use with a non-threaded bolt, but rather are used to fasten parts together. Each device requires threads on the bolt so that the plate member can engage the threads. The patent does not describe the device as being releaseably attachable to a non-threaded bolt of the type used with electronic seals of the type described hereinabove as an electrical connector. Further, the use of a threaded bolt is not desirable in a locking seal of the type described herein as such threads would permit the bolt to be readily disengaged and defeat the purpose of the seal which is to provide permanent locking engagement with the bolt and tamper evidence should the seal be opened.
U.S. Pat. No. 3,275,736 discloses interconnecting elements for use with electronic components. The disclosed elements employ thin conducting material provided with spring fingered openings fitting over and locking on to component lead wires. After the circuit is mechanically locked to the wires, the points of the spring fingers may be welded to the wires. However, the pointed ends of the fingers prevent the member from pulling off the leads because the pointed ends of the fingers dig into the leads. Thereafter, a resistance weld is formed at the pointed ends between the leads and the fingers. This device is not useful with the above described seal.
U.S. Pat. No. 3,745,513 discloses a strain relieving electrical connector. The connector has two loops each of which is soldered to a respective printed circuit board and to a component lead. The two loops are connected by a flexible member which minimizes force applied to the solder joints under dynamic loading conditions. One loop has a serrated opening. The point like tips of the serrations are biased into the component lead preventing the loop 16 from backing off from the lead. Such prevention is not desired in an electronic seal.
In the aforementioned copending application Ser. No. 09/293,135, an electronic security seal is disclosed for use with a bolt. The bolt is steel and has a head at one end of a shank. An insulated coating is over the shank except for the head and the end portion opposite the head which are bare. An electrically conductive coating covers the insulation and the head excluding the bare end. The electrically conductive coating forms a single conductor with the underlying metal bolt between the bolt head and the bare bolt end distal the head. The bare bolt end forms a first terminal and the electrically conductive coating at a region spaced from the bare end forms a second terminal. A protective second insulating coating is over the electrically conductive coating. First and second electrically conductive spring metal contacts in the disclosed seal are in ohmic contact with the respective first and second terminals forming a circuit therewith.
In use, the bolt is inserted into the seal housing along the bolt longitudinal axis and locked to the seal by a locking mechanism. As a result, the bolt makes sliding engagement with the contacts as the bolt is inserted into the housing. Presently, the disclosed contacts in that application are S-shaped and make sliding engagement with the bolt terminals at one tangential side of the bolt. This contact arrangement is not satisfactory as vibrations may cause intermittent engagement of the contacts with the bolt, which intermittent engagement may cause the seal to erroneously transmit a false tamper condition due to the break in the circuit.
None of the disclosed connectors described in the above prior art patents are useful with a cylindrical member and electronic seal of the type described herein. They either require threads or have points or edges which serve as a one way clutch by digging into the mating bolt, stud or screw. This digging prevents the mating component from backing off the bolt, stud or screw once inserted. Such digging is not permitted with a bolt or cylindrical coated member of the type described above for use in the seal of the aforementioned patent application. Such digging will destroy the integrity of the connection to the coating forming the second terminal and may ohmically engage the underlying bolt forming the first terminal.
A need is seen for an electrical connector for use with a cylindrical member in an electronic seal wherein the member has an electrically conductive coating forming a terminal. A need is seen for an electrical connector which will overcome the intermittent problems of prior art contacts and yet not damage the terminals on the coated member in the manner described.
A connector according to the present invention is for electrical connection to a cylindrical metal member having at least one electrical terminal surface and a longitudinal axis. The connector comprises a metal element having an opening for receiving the member therethrough. At least one resilient electrical contact extends from the element and overlies the opening, the member for passing through the opening in an insertion direction along the axis. The member at least one electrical terminal surface is for slidable releasable ohmic engagement with the at least one resilient electrical contact with negligible damage to the at least one electrical terminal surface. An electrical terminal is connected to the element.
In one aspect, a plurality of the at least one electrical contact extend from the element in an array about the opening. Preferably the contacts are identical.
In a further aspect, the at least one contact has a bent curved portion for slideably ohmically engaging a received bolt surface in two opposing directions.
Preferably the at least one contact and terminal are sheet metal one piece and integral with the element.
In a further aspect, the at least one contact extends from the element from a linear junction with the element to permit bending of the at least one contact adjacent to the junction.
In a further aspect, an array of at least three of the at least one contact are arranged about the opening.
In a further aspect, the element is planar, the terminal comprising one piece integral sheet metal with the element, the terminal comprising an L-shaped member with a first leg extending radially away from and coplanar with the element and a second leg extending from the first leg at a right angle to the first leg, a depression in the two legs forming a reinforcement rib to stiffen the second leg relative to the first leg.
In a further aspect, at least one terminal tab extends from the second leg normal to the second leg in a direction away from the element.
In a further aspect, the element is a sheet metal ring.
In a further aspect the element is a U-shaped yoke.
In a still further aspect, an electronic seal according to the present invention comprises an electrically operated seal device including an electrical connector and a circuit coupled to the connector for generating signals manifesting a seal tampered state and a seal closed locked state. A cylindrical member is included and includes electrically conductive means, the member for locking engagement with the device to place the device in the locked state, the electrically conductive means for causing the circuit to be energized for generating the signals after the member is placed in the locked state, the electrically conductive means when opened for opening the circuit to cause the circuit to generate the tampered state, the electrically conductive means when damaged making the circuit inoperative.
The electrical connector electrically connects the cylindrical member to the circuit in the locked state. The connector comprises at least one metal element having an opening for receiving the cylindrical member therethrough. At least one electrical contact extends from the at least one element and overlies the opening for resiliently slidably receiving the cylindrical member extending through the opening and for slidable releasable engagement with the member in the member insertion engaging direction with negligible damage to the electrically conductive means. An electrical terminal is connected to the element, the at least one contact and the terminal for connection to the circuit to enable the causing.